Lena Dunham and Laura Dern might be the most courageous women on TV and not just because the characters they play on their respective HBO comedies are brave enough to make fools of themselves with such determination.

Dern is the star and co-creator with Mike White of "Enlightened," while Dunham is the star and creator of "Girls," both of which make early second-season returns to HBO Sunday, thanks to the cancellation of David Milch's "Luck," which left a hole in HBO's winter schedule.

Dunham's Hannah Horvath and Dern's Amy Jellicoe may seem on the surface to have little in common. Hannah, a would-be writer, is nothing if not completely grounded and self-aware. She doesn't suffer fools gladly, even when she's the fool in question. It's because she's so driven that she is often blinded to what others really want from her or feel toward her.

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'Girls'

When: 8 p.m. Sunday

Network: HBO

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'Enlightened'

When: 8:30 p.m. Sunday

Network: HBO

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Amy, after a nuclear meltdown at work and subsequent time away at a Hawaii-based retreat, has pinned her life on a shaky belief that, having become "Enlightened," she can effect positive change in everyone around her and in the world in general. The last thing anyone would accuse her of is self-awareness. As much as she tries to adhere to vaporous pseudo-spirituality, her all-too-human side rears its uninvited head at the most inopportune moments.

Hannah lives in a cheap New York apartment she's sharing with her gay college ex-boyfriend Elijah (Andrew Rannells, "The New Normal"), while Amy lives in a sun-filled California tract house with her judgmental mother, Helen (Diane Ladd, Dern's real-life mother).

Hannah endures one low- or nonpaying job after another trying to get a foothold on a career as a writer, while Amy has returned to her old company but has been relegated to the basement and a tedious data-entry job along with other misfits, including Tyler (co-creator White) and their boss, Dougie (Timm Sharp), who dresses like Dirk Diggler and doesn't realize he'll never even make middle management in the company.

As different as they are, Hannah and Amy share a fundamental bravery that enables them to survive while the rest of the world seems ever-poised to stop them in their tracks.

Dern and Dunham are pretty brave as well, not only in creating their characters in the first place, but being able to defy the odds by taking high-concept, one-of-a-kind half-hour comedies and create second seasons without stumbling. In fact, if anything, the new seasons of "Girls" and "Enlightened" are even better than their premiere runs.

"Girls" is the better known of the two shows, with Dunham getting nominated for all kinds of awards for a show in which she bares all, in more ways than one. As the new season begins, her longtime best friend, Marnie (Allison Williams), has moved out after breaking up with her boyfriend, Charlie (Christopher Abbott). Hannah is still sort of seeing Adam (Adam Driver), who was hit by a bus at the end of last season, but she also has a thing going with Sandy (Donald Glover, "Community"). She insists she doesn't even think of him as black, but his Republican politics are another matter altogether.

Her posh poseur pal, Jessa (Jemima Kirke), has married a rich older man, while sweetly clueless Shoshanna (Zosia Mamet), having finally lost her virginity to Ray (Alex Karpovsky), is finding herself just as unsure about taking the next step in modern dating-slash-hookups as she was taking that first one.

The entire constellation of impetuous, ambitious, determined and insecure young urbanites in "Girls" is realigning in the new season, but at no point in the four episodes sent to critics do you feel that any of it is artificial. In a lesser show, second-season breakups and hookups often feel inauthentic. Not so with "Girls": What happens to Hannah and her circle is always credibly rooted in their characters.

Meanwhile, in LA…

Amy Jellicoe is doing marginally better at controlling her leftover rages as the second season of "Enlightened" begins, but she's still out for revenge against Abaddon Industries and still not getting that her crusade doesn't quite jibe with her new-found enlightenment. In the first season, Amy's thirst for vengeance prompted her to ram her car into her former boss' (and former lover's) car, among other things. This season, apparently having learned to control her temper, she's determined to bring the company down in other ways, by enlisting a Los Angeles Times investigative reporter (Dermot Mulroney) to blow the lid off Abaddon's business practices.

Fans of "Enlightenment" know that one of the recurring images in the show is the elevated footbridge that Amy crosses every day to get to the Abaddon high-rise, a gleaming fortress not unlike Cinderella's Castle at Disneyland. The bridge could be said to represent Amy's belated belief in a kind of fairy tale of her own existence. She has no idea how much she's disliked by her co-workers, including women she thought of as friends when she was an Abaddon executive. She is determined to have an abiding belief in happy endings, not only for herself, but for others, but she's not quite there yet and may never be. Time after time, she faces disappointment, but her way of surviving is not to allow it to register.

Self-delusion can grow fairly tiresome, in life and on TV, but what makes Amy sympathetic is that even though she almost convinces us at times that her personal fairy tale actually makes sense, we are always aware of her basic decency and, more important, her vulnerability.

Amy and Hannah are singular blends of driven focus and inner doubts. Hannah mines her doubts for strength and determination as she seeks the truths of her life, while Amy battles her doubts to re-enforce her resolve. For viewers, the results are the same: Two fascinating and complicated modern women, making their distinctive mark in the world, whether the world knows it or not.